Alkanes Flashcards
What are alkanes?
Alkanes are saturated hydrocarbons
Why are alkanes considered saturated hydrocarbons
This is because all the carbon atoms are bonded with single bonds and there are no double or triple bonds
What is the main source of alkanes?
The main source of alkanes is crude oil
What is the general formula for alkanes?
The general formula for all chain alkanes is CnH2n+2
Why are unbranched alkanes not actually straight?
The C - C - C bond angle is 109.5 degrees, which gives the chain a zigzag shape rather than a straight line
Why are alkanes considered almost non - polar?
Alkanes are almost non - polar because the electronegativities of carbon (2.5) and hydrogen (2.1) are very similar
How does the size of an alkane molecule affect the strength of van der Waals forces?
The larger the alkane molecule, the stronger the van der Waal forces
How does the weak polarity of alkanes affect their physical properties?
Since alkanes have weak van der Waals forces it leads to low boiling and melting points compared to more polar molecules of similar size
What is the relationship between the molecular size of alkanes and their boiling point? Explain why.
The larger the molecular size of an alkane, the higher the boiling points due to the increased strength + number of the van der Waals forces
Why do the boiling points of alkanes increase as the chain length increases?
As chain length increases, the intermolecular van der Waals forces become stronger, requiring more energy to overcome
At what chain length do alkanes become solids at room temperature?
Alkanes with about 8 carbon atoms become solids at room temperature
How do the boiling points of branched alkanes compare to straight chain alkanes with the same number of carbon atoms?
Branched alkanes have lower boiling points than straight chain alkanes with the same number of carbon atoms
Why do branched alkanes have lower boiling points than unbranched alkanes?
Branched alkanes cannot pack as closely together, making the van der Waals forces less effective
Why are alkanes insoluble in water?
Water molecules are held together by strong hydrogen bonds, which are much stronger than the van der Waals forces acting between alkane molecules
What type of liquids do alkanes mix well with?
Alkanes mix with other relatively non - polar liquids
Why are alkanes relatively unreactive?
Alkanes have strong carbon - carbon and carbon - hydrogen single bonds, which require a lot of energy to break
